Circuit breakers



FIG. I

INVENTOR ALFRED E. MAIER AT TORNEY 3,002,068 g i V V CIRCUIT BREAKERSAlfred E. Maier, Colonia, N ..I., assignor to Federal Pacific ElectricCompany, a corporation of Delaware 7 Filed Aug. 4, 1960, Ser. No. 47,4358 Claims. (Cl. 200-88) The present invention relates to electricswitching apparatus, more particularly to manually operated circuitbreakers having an over-centering toggle for operating the movingcontact assembly and an over-current release arrangement for controllingthe toggle.

Circuit breakers of this type have been known and used for severaldecades. To increase the current-carrying capacity it is understood thatthe sizeand strength ther, a single operating mechanism is commonlyemployed to operate multipole circuit breakers. The moving contacts areon a common shaft and (due to minor misalignment) one moving contact mayengage its companion stationary contact slightly ahead of the movablecontacts in the other poles. 'The overtravel spring in each pole takesup any such disparity and insures contact pressure in each pole. Arcingat the contacts may also cause dimensional changes by erosion of thecontacts. The overtravel spring accommodates such contact dimensionalvariations.

The contacts initially come into engagement. before the toggleover-centers, and the over-centering operation builds up stress in theovertravel spring. If higher operating currents dictate a substantialincrease in contact pressure, a correspondingly strongercontact-overtravel spring is required and correspondingly increasedstrength of the over-centering spring is needed.

In a toggle mechanism, the use of heavier or stronger springs tend toimpose heavier bearing stresses and to create greater amounts offriction at the joints of the toggle, which increases still further therequired strength of over-centering toggle-operating spring. Increasedbearing friction also reduces the sensitivity of the toggle as itapproaches and reaches dead-center in the contact-closing direction.

' 'In a common type of mechanism the over-centering springs areconnected between the knee of the toggle and the operating handle.Over-centering of the toggle is insured despite bearing friction andheavy overtravel springs by driving the handle ends of theover-centering springs beyond dead-center relative to the toggle UnitedStatesPateht O links. For overcoming both a stronger over-travel springand an increase in friction at the toggle bearings, the handle wouldordinarily have to be operated considerably beyond that corresponding todead-center position of the toggle. the handle, and greater elongationof the springs.

This involves a longer operating stroke for The fact that the springsmust be elongated farther than would be the case with only a nominalamount of bearing friction and only a minimum strength of contactover-travel springs tends to limit the maximum stiflness of thespringsthat can be used with the usual mechice more powerful mechanismthat acts with a clean-cut snap when the toggle is over-centered.

It is accordingly an object of the present invention to improveover-center spring mechanisms in order to enable springs of increasedstifiness to be used.

Mere increase in the strength of springs used might be achieved withlarger springs. Space limitations may prevent this. In the novelembodiment of this invention detailed below, increased spring strengthis realized 7 without resort to over-size springs by reducing the extent of elongation required, thereby making possible the ueof relativelysmall springs of such stiffness that their elastic limit might well beexceeded if the usual clongation were needed.

A feature of this invention resides in provision of a novel mechanismthat minimizes the required elongation of the over-centering springswhen the mechanism ,is'operated in the contact-closing direction.

More particularly it is an object of this invention to improveover-centering spring-and-toggle circuit breaker mechanisms by reducingthe required spring elongation in its contact-closing operation, withouthowever reducing the desired extent of collapse of the toggle incontact-opening operations and without interfering with the resultingoperation of the circuit breaker by the 0pf crating handle, and withoutdisturbing the trip-free" contact-opening operation of the toggle isincreased by an increase in the required handle travel beyonddeadccnter" in the on direction. Accordingly another object of theinvention is to improve circuit breakers having overtravel springmechanisms by minimizing the required over-center travel of theoperating handle.

Excessive elongation of the over-center spring has the further effect ofunduly increasing the required manual operating efiort. It alsoincreases the length of slot provided in the circuit breaker cover forthe operating handle, a change thatvis undesirable for many reasons.

Accordingly, it is a broad object of the present invention to improvecircuit breakers having over-center spring mechanisms with a view tominimizing the foregoing limitations resulting from the use of springsof increased stiffness. This and other objects of the invention areaccomplished in the illustrative circuit breaker described below as anembodiment of the invention in its various aspects. The illustrativecircuit breaker includes a positive drive coupling between the operatinglever and the knee of the toggle, arranged for mechanically driving thecollapsed toggle in the contact-closing direction part-way toward itsdead-center condition. More particularly, a bail is pivoted to themanual operating lever and is guided to engage and drive the knee of thetoggle in the operating on" stroke of the manual operating lever forpicking up and driving the toggle part-way to the dead-centeredconfiguration. During this positive drive, the burden on the operatingsprings is held to a minimum. Moreover, since the knee of the toggle isshifted toward the deadcenter configuration, the degree ofover-centering and elongation of the springs required to induceover-centering of the toggle and snap-action closing of the contacts isminimized, and stifler springs can be used Without increase in spacerequirements. Still further, by minimizing the extent of over-centeringof the springs in relation to the Patented Sept. 26, 1961 K 3 toggleduring a contact closing operation, the reverse operation of the circuitbreaker is improved for both manual opening and for automatic overloadrelease of the circuit breaker. High contact pressure and powerfulcontact opening bias become available through the use of stiffer springswithout, however, the attendant disadvantages heretofore described.

The nature of the invention in its various aspects and further objectsand features of novelty will be better appreciated from the moredetailed description of the illustrative embodiment below, in whichreference is made to the accompanying drawings. In those drawings:

FIG. 1 is a side view of a circuit breaker embodying the invention shownin the open configuration of its operating mechanism with portions beingbroken away and others shown in section for purposes of clarity;

FIG. 2 is a fragmentary view similar to FIG. l showing the operatingmechanism in the configuration it assumes just prior to snap-closing ofthe contacts, the relative position of the contact arm also being shownin broken lines in the open configuration of FIG. 1;

FIG. 3 is a detail view of the closed contacts and the moving contactsupport viewed as in FIGS. 1 and 2; and

FIG. 4 is a fragmentary cross-section of the operating mechanism viewedfrom the line 4-4 in FIG. 1.

-Referring to the drawings, the circuit breaker mech anism is enclosedin a molded case including a cover and a base 12. A circuit through thecircuit breaker '(when it is closed) extends from one terminal 14 to thestationary contact 16, thence to movable contact 18, along conductiveflexible braid and metal bar 22 to the opposite terminal 24. Movablecontact arm 26 which carries contact 18 is carried by pivot 44 incontact arm carrier 28, and biased by compression springs 29 in thedirection to build up contact pressure when the contacts are closed(FIG. 3). Where the contacts are open, the swing of contact arm 26 isenforced by spring 29 and is limited by engagement of portion 26a of thecontact arm with the bottom edge 28a of the channel-shaped contact armcarrier 28. Contact arm carrier 28 is afiixed to the insulated shaft 30the ends of which are pivoted in corresponding bearing portions of themolded base 12. Plural contact arm carriers 28, with respective contactarms 26, are mounted on the aforesaid shaft for coordinated operation ofthe contacts of a multi-pole circuit breaker.

An over-centering spring mechanism is provided for operating thecontacts between the closed and open positions and for effectingautomatic release and opening of the contacts in response to anoverload. The operating mechanism includes a manual operating lever 32and handle 33. Lever 32 is pivoted at its lower extremity in a fittedframe 34. An overload release member or cradle 36 has a pivot 33 fixedin the frame 34. A pair of toggle links 40 and 41 are pivotallyconnected to each other at knee 42. These toggle links have a top pivot43 and a bottom 44 pivot in members 36 and 28. Where there are pluralcontact carriers 28, for a corresponding number of poles, there is here(as is usual) only a single operating mechanism for all of the contactsoperated by square shaft 30. Two pairs of springs 45 extend betweenmanual lever 32 and the knee 42of the toggle although only one pair isvisible in FIGS. 1 and 2.

The right hand extremity of cradle 36 is normally restrained by a latchroller 46 carried by a common trip bar 48 that extends across all of thepoles (where there are plural poles). A spring lever 49 biased upwardlyby spring 50 and counterclockwise about its pivot is normally restrainedby a combined ambient temperature compensating bimetal and latch 52which has a stationary pivot near its lower end. A current responsivebimetal 54, adapted to be heated by flow of current through bar 22, isarranged to flex upward when heated. The upward deflection of bimetal 54pivots latch 52 clockwise in a direction to release spring lever 49,thus operating trip bar 48 and latch roller 46 so as to release cradleas when over-current conditions heat bimetal 54 sufficiently. A magnetictripping arrangement, including pole structure 56 and armature 58, isalso arranged to drive latch 52 clockwise in the releasing direction,this magnetic arrangement operating in response to instantaneous severeoverload currents. The right-hand extremity of armature 58 underlies aportion of latch 52, as shown, and spring 59 biases the armaturecounterclockwise about its pivot.

The circuit breaker is illustrated in FIG. 1 in its open condition, withcradle 36 latched so that the mechanism is in condition for driving thecontacts closed when operated. This is accomplished by moving manuallever 32 to the left in the drawings. The upper ends of tension springs45 are correspondingly shifted to the left, and when the resultingspring tension through knee 42 is shifted so as to act along the line tothe left of the upper pivot 43 of the toggle in cradle 36, the knee isbiased to the left and tends to straighten the toggle. This occurs witha snap-action, and suddenly drives the contact carrier .28 in theclosingdirection driving movable contact 18 against the stationarycontact to and increasing the stress in overtravel spring or springs 29(in the case of multiple poles). 4

When the contacts have been closed in this manner, the line of upwardthrust through knee 2 passes to the left of the upper toggle pivot 43 incradle 36. In the event of an over-current, cradle 36 is released forcounterclockwise swing about pivot 38, and the upper toggle pivot 43shifts to the left and across the resultant line of action of thesprings 45. When this takes place, the tensioned overcenter springs 45are free to cause sudden collapse of the toggle and correspondingly, tolift the various contact oarriers 28 as a unit from their closedposition. I

The action of' the toggle mechanism, including the toggle links and theover-centering spring arrangement, which should be firm andquick-acting, is dependent upon the various masses involved and is alsodependent upon the strength of the springs. For circuit breakers ratedfor large currents, firm contact pressure and relatively large contactsare needed, and strong over-center springs are desirable. This producesa tendency toward significant and potentially troublesome friction atknee 42 as well as at the upper pivot 43 of the toggle. In order toovercome this friction, it might be possible to provide increased roomfor handle 33 and manual lever 32 to move further to the left in the onposition in order to increase the extent of over-centering of thesprings beyond the line between knee 42 and upper pivot 43 of thetoggle. Where the space for such additional movement is limited the gainis marginal and there is danger that the mechanism will not becomeover-centered and that therefore the contacts 16, 18' will remain open.However, even if such provision is made, there is still considerabledanger of permanently deforming the springs 45 due to the increasedelongation caused by the longer stroke of the handle 33 while the knee42 of the toggle remains close to its original position as illustratedin FIG. 1. The additional stretch of the springs 45 could of course beaccommodated without damage to the springs by employing springs that arerelatively soft and therefore readily capable of considerable elongationwithout permanent deformation. However, this would defeat efforts toincrease the circuit breaker rating and accordingly it is important thatthe strongest springs practicable be used.

The foregoing mechanism is greatly improved through the provision of abail 60 pivoted at its extremities to manual lever 32. The bail shown isgenerally U-shaped member having a bight portion formed to engage theknee 42 of the toggle during part of the toggle erecting motion of lever32. A pair of guide projections 62 extend, integrally, from fixed frame34, and limit the clockwise motion of the bail. While gravity normal-1ymaintains ball 60 in engagement with guide projections 62, the bail isalso effective even if the breaker were mounted unnaturally in invertedposition, since, when the manual lever spogoas 3b. is operated the bailis still constrained against the toggle close to the knee by closespacing between the cradle. and the bight of bail 60. v

. When handle 33 of the circuit breaker is moved toward the left in thecontact-closing direction, bail 60 is operated by lever 32 in thedirection to drive the toggle knee 42 in the toggle erecting orstraightening direction. At the same time, the line of action of theovercenter springs 45 shifts down with a snap, forcing the movablecontacts 18 against the fixed contacts 16. Over'centering movements oflinks 40and 41 carry the toggle away from bad 60. The extentofover-centering of the mechanism is limited by engagement of the toggleknee 42 with the portion of treleasable member 36 adjacent to its pivot38. It is relatively easier toovercome the friction of the toggle pivotsin erecting the toggle from the configuration in FIG. 3 than from thatshown in FIG. 1. For this reason the snap operation ofthe toggle, forclosing of the contacts, occurs when the line of action of the springs45 has traveled only a short distance beyond dead-center. ;,,Were bail60 omitted, it wouldbe necessary ,for the handle to move considerablyfarther to the left in order to reach and then insure over-centering ofthe toggle links fromtheir position illustrated in FIG. 1. This in turnwould require substantially greater elongation of the springs andthereby impose a limitation on the stiffness of the springs which couldbe used. Softer springs, it will be appreciated, tend to reduce theavailable contact pressure that can be built up at the contacts, whenclosed, and to reduce the speed of opening of the contacts. Soft springslimit the mass of the moving contact structure that can be. operatedwith the quick motion that is especially desirable in the openingdirection for effective current interruption.

Where the end position of handle 33 is achieved with only a minimum ofover-travel beyond dead-center, it becomes possible to utilize only aminimum of counterclockwise swing of cradle 36 for shifting the upperpivot 43 of the toggle to the left (in the toggle collapsing direction)Consequently, a greater speed of response of the overload-releasemechanism may be expected than in the case where bail 60 is omitted anda longer overcentering travel of the handle is involved.

Cradle 36 is shifted counter-clockwise about its pivot when released byoperation of the trip mechanism, due to the action of tension springs 45in urging the entire toggle upward. With the improvement afforded bybail 60, it is feasible to minimize the swing of cradle 36 in anoverload-release operation. This means that most of the stored energy inthe springs 45 is conserved for lifting the contact carrier 28 quicklyand thus driving the contacts 16 and 18 apart. It is important toconserve the spring effort available for opening the contacts in View ofappreciable increases in mass of contacts 18, contact arms 26, and braid20 that may be occasioned by higher current ratings. g

The circuit breaker is trip-free, in that the mechanism is entirely freeto open the circuit even if the handle 33 should be operated and thenheld in the closed position while over-current-release takes place.Notably, the addition of bail 60 does not in any way interfere with theopening operation of the breaker, either naturally or under overloadrelease conditions. When the breaker is opened unnaturally, it isevident that lever 32 shifts bail 60 out of position in which it mightobstruct collapsing motions of the toggle. When handle 33 is naturallyheld on during an automatic overload release operation, bail 6 60 doesnot interfere with the contact-opening operation of the contacts. Thisis because the principal motion of the toggle links is bodily upward andthere is only a limited movement of the toggle links toward bail 60while cradle 36 remains in its released condition and the handle is inits on position. When the handle is returned to off and therebeyond toreset position, the toggle merely approaches bail 60 as it resumes theconfiguration of FIG. 1. g

In FIG. 2 the position of contact arm 26 in solid lines represents thecondition of the contact arm just prior of I open position of thecontact arm (as in FIG. 1).

the over-centering of the springs in relation to the upper toggle link40, and the dotted lines represent the fully In practice this is of noconcern, and satisfactory operation of the apparatus is not impaired,since the gap between contacts 16 and 18 is ample until the actualsnap-closing operation occurs.

Description of certain portions of the illustrative mechanism have beenomitted, deliberately excluding details which might conceiveably be ofinterest, in as much as those details are apparently unnecessary to anunderstanding of the present invention. For example, the overcurrentrelease mechanism illustrated is more fully described in copendingapplication S.N. 852,013, filed November 10, 1959, assigned to theassignee hereof. I

The nature of the invention and various adaptations and modificationswill be readily appreciated by those skilled in that art in view of theforegoing description of the illustrative embodiment; and it istherefore appropriate that the invention should be broadly construed inaccordance with its full spirit and scope. What is claimed is:

1. Switching apparatus including companion contacts, a movable contactmember carrying one of said contacts, a pair of toggle links pivoted toeach other at a knee and including one link pivoted to said movablecontact member for effecting operation thereof, amanual operating membermovable between open and closed" positions, a spring connected to theknee of the toggle and arranged to be overcentered relative to the otherspring mechanism connected to said mova'ble contact member, saidmechanism including an operating member 'movable between open and closedpositions, a spring operable overcenter by said operating member forbiasing the contacts open and closed correspondingly, and a partoperable by said manual operating member in positive driving relation tothe remainder of said overcentering mechanism during only an initialportion of the movement of the operating member from open toward closedposition thereof.

3. A circuit breaker including companion contacts, a movable contactmember carrying one of said contacts, a pair of toggle links foroperating said movable contact member, a releasable member andover-current releasing means normally effective to latch said releasablemember, an operating member movable between open and closed positions, aspring connected to the knee of the toggle and to said operating member,respectively, the extremities of said toggle being pivoted to saidreleasable member and to said movable contact member respectively, and abail pivoted to the operating member and having a bigh't portion formedto engage the knee of the toggle in the toggle erecting direction duringonly a portion of the closing operation of the operating member.

4. A circuit breaker including companion contacts, a

movable. contact member carrying one of said contacts, a pair of togglelinks for operating said movable contact member, a releasable member andover-current releasing means normally effective to latch said releasablemember, an operating member movable between open and closed positions, aspring connected to the knee of the toggle and to said operating member,respectively, the extremities of said toggle being pivoted to saidreleasable member and to said movable contact member respectively, and abail pivoted to the operating member and a bight portion formed toengage the knee of the toggle in the toggle erecting direction duringonly a portion of the closing operation of the operating member, saidreleasable member in its latched condition being disposed adjacent saidbail so as to guide the latter toward the toggle knee.

5. A circuit breaker including companion contacts, a movable contactmember carrying one of said contacts, a pair of toggle links foroperating said movable contact member, a releasable member andover-current releasing means normally effective to latch said releasablemember, an operating member movable between open and closed positions, aspring connected to the knee of the toggle and to said operating member,respectively, the extremities of said toggle being pivoted to saidreleasable member and to said movable contact member respectively, andpositive drive means mounted on said operating member and engageablewith the toggle in driving relation thereto during only part of themovement of the operating member from open toward closed positionthereof for operating the toggle links from their collapsed positiontoward an erected position.

6. A circuit breaker including companion contacts one of which isafiixed to a movable contact member, a pair of toggle links foroperating said movable contact member, a fixed frame, a releasablemember pivotally mounted on said fixed frame and over-current releasingmeans normally effective to latch said releasable member, an op eratingmember pivotally mounted on said fixed frame for movement between openand closed positions, a spring connected to the knee of the toggle andto said operating member, respectively, the extremities of said togglebeing pivoted to said releasable member and to said movable contactmember respectively, a bail pivoted to said operating member andengageable with the toggle in driving a relation thereto during movementof the operating 111cmher from open to closed position thereof foroperat ing the toggle links from their collapsed condition toward anerected position, and means mounted on said fixed frame for guiding saidbail into engagement with said toggle.

7. A circuit breaker including a releasable member, over-current controlmeans normally effective to latch said releasable member, a pivotedcontact arm, a pair of toggle links pivoted to each other at a knee andpivoted respectively to said releasable member and to said movablecontact member, a manual operating member movable between an open and aclosed position, a tension spring between said toggle knee and saidmanual operating member said spring being arranged to act substantiallyalong the line passing through the knee of the toggle and the pivotpoint of the toggle and releasable member, nd positive drive meansmounted on said operating lever for contacting said toggle mechanismadjacent said knee and assisting said toggle in the erecting directiononly to a partially erected position upon operation of said manualoperating member from said open to said closed position, said positivedrive means functioning only prior to said spring passing over theaforesaid line.

8. In a circuit breaker having over-current control means thecombination comprising, a fixed contact, a movable contact, a pivotedcontact carrier supporting the movable contact for cooperation with saidfixed contact, a releasable member normally latched in position by saidover-current control means, a pair of toggle links pivoted to each otherat a knee and pivoted respectively to said releasable member and saidcontact carrier, a manual operating member movable from an open to aclosed" position, a tension spring between said toggle knee and saidmanual operating member, said spring adapted to move said kneeover-center of the line between the other pivot points of the togglefrom a position closely adjacent thereto, positive drive means mountedon said manual operating member for delivering aid knee to said positionadjacent said line only when said operating member is moved from saidopen position toward said closed" position to erect said toggle.

No references cited.

Disclaimer 3,002,068.--rilf1ed E. Maz'ew, Colonial, N .J CIRCUITBREAKERS. Patent dated Sept. 26, 1961. Disclaimer filed Dec. 12, 1962,by the assignee, Federal :Pacz'fia Electm'c Company. Hereby enters thisdisclaimer to claims 1 and '2 of said patent.

[Ofiicial Gazette J anuamy 22, 1963.]

Disclaimer 3,002,068.rilfred E. Maz'ev', OOIOIliZL, N .J CIRCUITBREAKERS. Patent dated flSept. 26, 1961. Disclaimer filed Dec. 12,19612, by the assignee, Fecleml Pacific Electric Company. Hereby entersthis disclaimer to claims 1 and 2 of said patent.

[Ofiicz'al Gazette J (mm/my 252, 1.963.]

